The great secret that all old people share is that you really haven't changed in seventy or eighty years. Your body changes, but you don't change at all.
To fulfill the highest most truthful expression of yourself as a human being. You want to max out your humanity by using your energy to lift yourself up, your family and the people around you.
A writer is a person who is not satisfied with the world as it is, who wants to change it, to improve it, to make it more beautiful, more just, more livable.